Method for assembling a pneumatic booster

ABSTRACT

A device ( 100 ) for assembling a pneumatic booster ( 200 ). A cover ( 203 ) of the booster is housed in a support ( 101 ). A cylindrical cap ( 104 ) whose internal volume ( 107 ) is greater than a volume of a cylinder ( 206 ) of the booster, covers the cylinder placed on the cover. A gearing element ( 110 ) of the device rotates two sets of rollers ( 109 A and  109 B) about the booster. An eccentric ( 118 ) controlled by the gearing element allows an oscillating movement of the rollers against a wall of the booster. The swaging is achieved by alternately applying the rollers ( 109 A) and ( 109 B). An angle of attack ( 114 A) of the first rollers is greater than an angle of attack ( 114 B) of the second rollers. The invention also relates to a method of swaging a booster and such a booster.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of co-pending U.S. patent applicationSer. No. 10/581,837 filed on Jun. 5, 2006, which is a national stagefiling under 35 U.S.C. 371 of International Application No.PCT/EP2004/014280, filed Dec. 15, 2004, which claims priority to FrenchPatent Application No. 0315495, filed Dec. 24, 2003, the disclosures ofwhich are incorporated by reference herein in their entireties. Priorityto each application is hereby claimed.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a device for assembling a pneumatic booster ofa motor vehicle braking device. More precisely, the invention relates toa device making it possible to fixedly attach a cover and a cylinder ofa pneumatic booster. The invention also relates to a method making itpossible to assemble the cylinder and the cover by using the device ofthe invention. The invention finally relates to a pneumatic booster.

One object of the invention is to provide a booster that can be usedsafely in a braking device. Another object of the invention is toprevent a disassembly of the booster during its use, irrespective of thethickness of a metal sheet forming the booster. An additional object ofthe invention is to provide a booster that is lightweight, without itsstrength being affected.

In a motor vehicle braking device, a booster may be mounted between abrake control and a master cylinder. The pneumatic booster has the roleof amplifying a force at the brake control, so that a hydraulic pressurein the master cylinder is greater.

A booster may be furnished with a generally cylindrical-shaped casing.The casing is formed of a cylinder and a cover. The cylinder and thecover are fixedly attached to one another. A front chamber and a rearchamber are arranged in an internal volume of the casing. The frontchamber is directed toward the master cylinder, and has a variablevolume. The rear chamber, equally with a variable volume, is directedtoward the brake control. The front chamber is separated from the rearchamber by a movable partition. The movable partition is formed by asealed and flexible membrane and by a rigid skirt plate. The frontchamber is connected pneumatically to a vacuum source. The rear chamberis connected pneumatically, in a manner controlled by a valve, to asource of propelling fluid. A brake control actuates a control rod ofthe booster. The actuation of the rod controls the opening of the valveand an inflow of fluid into the rear chamber. The change of pressurethat results therefrom causes a movement of the rigid skirt plate.

During braking, wrenching forces exerted at the location of the boosterare extremely great. Specifically, the chambers of the booster aresubjected to sudden changes of pressure. In particular, during braking,air is allowed into the rear chamber. This inlet of air propels themovable partition toward the front chamber. Since the casing of thebooster is made of two originally independent parts, it is essentialthat these two parts are firmly fixed together. It is thereforenecessary that the contact between the cover and the cylinder issufficient so that, during braking and more precisely during thepropulsion of the skirt plate, the cylinder is not wrenched away fromthe cover.

In order to ensure that the cover is properly attached to the cylinder,spot swaging is currently carried out on an external periphery of thewalls of the cover and the cylinder. “Spot swaging” means swaging atlocalized points. In order to hold the cylinder firmly onto the cover,these swaging points are evenly distributed over the whole externalperiphery of the casing. Hitherto, such an assembly has been sufficient.

However, for some time, the search has been on to reduce the weight ofthe booster. Specifically, the booster and more precisely the boostercasing is formed of metal sheet walls. A thickness of the metal sheetand a shape of the booster therefore have an effect on its weight. Thesearch in particular is to reduce the weight of the booster by reducingthe thickness of the metal sheet forming the casing. The thickness andthe shape of the booster have been modified in order to obtain a minimumweight. “Minimum weight” means the lowest weight of the booster at whichthe same rigidity and the same resistance to wrenching as a conventionalbooster is obtained.

However, the breaking strength at the location of the join between thecover and the cylinder is reduced. A spot swaging of the cover with thecylinder therefore does not provide full satisfaction when the thicknessof the metal sheet is greatly reduced.

The invention seeks in particular to solve this problem by providing abooster whose thickness and shape may be modified in order to obtain aminimum weight. The booster obtained is such that it has a greatresistance to wrenching, including at the location of the join betweenthe cover and the cylinder of the casing.

For this, the invention proposes a device for assembling a booster andmore precisely a cover and a cylinder of a casing of the booster. Theassembly device of the invention allows a continuous swaging, over thewhole external periphery of the casing, of the cylinder and of thecover. Continuous swaging makes it possible to obtain a strong hold ofthe two parts, one on the other. The zone of contact offers a betterresistance to the wrenching forces.

To achieve such a continuous swaging, the device of the invention isfurnished with at least one set of rollers. The rollers are rotatedabout the booster. The rollers come into contact with the booster at thelocation of the join between the cover and the cylinder of the casing.The rollers, when they pass, fold one end of a metal sheet forming thewall of the cylinder around an end of a metal sheet forming the wall ofthe cover.

In a particular exemplary embodiment of the invention, the device isfurnished with two different sets of rollers. The first set of rollersmakes it possible to bend the end of the metal sheet forming the wall ofthe cylinder around the end of the metal sheet forming the wall of thecover, at a first angle. The second set of rollers, for its part, makesit possible to bend the metal sheet of the cylinder at a second, moreacute angle than the first. A roller of the second set of rollers is notpressed against the external wall of the casing until a roller of thefirst set of rollers has first passed.

Thus, the rollers of the first set of rollers begin to bend the metalsheet of the cylinder. The first bending action makes it possible tobend, from an initial position parallel to an axis of rotation of thedevice, the metal sheet by thirty to sixty degrees. The metal sheet isthus partially pushed inward in the direction of the center of thebooster. An initial position of the end of the wall of the cover isperpendicular to the end of the wall of the cylinder. “Initial position”means the position in which the cover and the cylinder are placed one onthe other, but not attached to one another. After the pass of at leastone roller of the first set of rollers, the metal sheet of the cylinderis folded back in the direction of the metal sheet of the cover, whichit swages lightly. A roller of the second set of rollers is then pressedagainst the metal sheet of the casing, where the first roller passed, inorder to further fold the metal sheet of the cylinder against the metalsheet of the cover. Ideally, the metal sheet of the cylinder is foldedninety degrees after the rollers of the second set of rollers havepassed.

The sets of rollers of the device of the invention are, for example,furnished with three rollers each. The rollers of the first set arealternated with the rollers of the second set. For an assembly device ofgenerally circular cylindrical shape, the rollers are distributed evenlyover a complete perimeter of the device. Thus, for example, a roller ofthe first set is separated by 120° from another roller of the first set.A roller of the first set is separated by 60° from a roller of thesecond set.

So that the swaging is carried out in two successive steps, the rollersof the second set must be pressed against the wall of the casing only atthe locations where the rollers of the first set have already passed.For this, in addition to a rotary movement of the rollers about thebooster, each of the rollers is forced to make an alternating radialmovement relative to the booster. Such an oscillating movement is madepossible by an eccentric mechanism of the assembly device. The rollersof the two sets are angularly out of phase with one another. The rollersof one and the same set are however angularly in phase. Thus, therollers of the first set and then the rollers of the second set arealternately brought toward the center of the booster. This is how toobtain a continuous swaging of the casing of the booster in one or morecomplete rotations of the rollers about the booster.

The invention also proposes a method of assembling the casing of thebooster. The method of the invention makes it possible to swage thecover and the cylinder of the casing in a continuous manner over thewhole external perimeter of the casing.

The subject of the invention is therefore a pneumatic booster for amotor vehicle braking device, characterized in that a cover and acylinder of said booster are attached to one another over a completeexternal contour.

A further subject of the invention is a device for assembling apneumatic booster, characterized in that it comprises

-   -   a fixed cylindrical support whose internal volume is greater        than the volume of a cover of the booster, the cover being        housed in the support,    -   a cylindrical cap whose internal volume is greater than the        volume of a cylinder of the booster, said cap imposing an axial        load on the cylinder,    -   at least one set of rollers, rotated by a motor, the rollers        rotating at least partially about the support.

An additional subject of the invention is a method of swaging a booster,characterized in that it comprises the steps

-   -   a cover of a booster is inserted into a support of a swaging        device, a top end of a wall of the cover resting on a top end of        an internal wall of the support,    -   a cylinder of the booster is placed on the cover, a bottom end        of a wall of the cylinder resting on the top end of the wall of        the cover,    -   a cap of the swaging device is placed on the support, a bottom        end of the cap compressing the bottom end of the wall of the        cylinder onto the top end of the wall of the cover,    -   a motor is actuated,    -   the swaging rollers are made to rotate about the booster, by        means of the motor,    -   the bottom end of the wall of the cylinder is swaged        continuously onto the top end of the wall of the cover.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood on reading the followingdescription and on examining the figures that accompany it. The latterare given as an indication and in no way limit the invention. Thefigures represent:

FIG. 1: A longitudinal section of a booster housed in an assembly deviceof the invention;

FIGS. 2( a and b): An enlargement of FIG. 1 at the location of aconnection between a cover and a cylinder of the booster, and of aroller of the invention;

FIG. 3: A cross section of an assembly device of the invention.

DETAILED DESCRIPTION

FIG. 1 shows an exemplary embodiment of a device 100 for assembling abooster 200. The device 100 is furnished with a fixed support 101. Inthe example represented in FIG. 1, the support 101 has a generallycylindrical shape. An internal volume 102 of the support 101 is suchthat it is possible to insert therein a rear portion 201 of the booster200. “Rear portion 201 of the booster 200” means a control rod 202 andcover 203 of the booster 200. The cover 203 also has a generallycylindrical shape.

One end 2004 of a wall 205 forming the cover 203 rests on a top end 105of a center positioner 106. The center positioner 106 is, for example,generally ring-shaped. A diameter of the ring 106 is approximately equalto an internal diameter of the support 101 in the location of a top end103 of the support 101. Thus, the center positioner 106 is placed in aninternal perimeter of the support 101 in the location of a top end 103.The center positioner 106 makes it possible to ensure a good positionfor the cover 203. “Good position of the cover 203 in the support 101”means a position allowing the device 100 to successfully assemble thebooster 200.

In another exemplary embodiment, the center positioner 106 consists ofat least two distinct parts. Thus, the center positioner 106 does notfully follow the internal contour of the support 101. It may be placedevenly, at different points on the internal diameter of the support 101.The various elements forming the center positioner 106 thus make itpossible to support the cover 203 at certain points and to center it. Inanother embodiment, it is also possible to use no center positioner 106.The cover 203 then rests directly on the support 101, at the location ofthe top end 103 of said support 101.

Once the cover 203 has been placed in the interior 102 of the support101, a cylinder 206 of the booster 200 is positioned. The cylinder 206forms a front portion of the booster 200. The cylinder 206 has agenerally cylindrical shape. The cylinder 206 is placed on the cover 203so that an end 208 of a wall 209 forming the cylinder 206 rests on theend 204 of the cover 203. In the example shown in FIG. 1, an end 211 ofa sealing membrane 210 of the booster 200 forms a fold 211. The fold 211is trapped between the ends 204 and 208 respectively of the cover 203 ofthe cylinder 206. The fold 211 particularly provides a seal at thelocation of contact between the cover 203 and the cylinder 206.

A cap 104 of the assembly device 100 is then placed on the support 101.The cap 104 is generally cylindrical in shape. An internal volume 107 ofthe cap 104 is such that the cylinder 206 can be housed therein. A firstend 108 of the cap 104 rests against the end 208 of the wall 209 of thecylinder 206. “First end” means in the description the end directedtoward the left in the figure. Conversely, “second end” means in thedescription the end directed toward the right in the figure. The end 108of the cap 104 is then pressed in a direction D onto the end 208 of thecylinder 102. This imposes an axial load at the location of theconnection between the cover 203 and the cylinder 206. The fold 211 iscompressed between the two walls 205 and 209 at the location of theirends, respectively 204 and 208.

Rollers 109 (two rollers visible in FIG. 1) are placed on an outerperiphery of the support 101. FIG. 3 shows more precisely thedisposition of the rollers 109 of the device 100. The rollers 109 aresix in number. Rollers 109A of a first set are interspaced with rollers1098 of a second set. The rollers 109 are placed evenly over the wholeperiphery of the support 101.

FIG. 1 shows that the rollers are in contact with the booster 200 at thelocation of the connection between the cover 203 and the cylinder 206.

FIGS. 2 a and 2 b show two enlargements, respectively an enlargement ofFIG. 1 at the location of contact between a roller 109A and the booster200, and at the location of contact between a roller 109B and thebooster 200. In both cases, it can be seen that the end 204 of the cover203 rests on the top end 105 of the center positioner 106. Similarly,the fold 211 of the sealing membrane 210, compressed between the end 204of the cover 203 and the end 208 of the cylinder 206 can be seen. Theend 208 of the cylinder 206 is compressed by the end 108 of the cap 104.The end 208 of the cylinder 206 is approximately parallel to an axis ofrotation of the center positioner 106. The end 204 of the cover 203, forits part, is perpendicular to the end 208. The end 208 extends towardthe right in FIG. 2 a beyond a point of contact with the end 204.

In the invention, the end 208 can be bent around the end 204 and thefold 211 so that the end 208 is ideally perpendicular to the axis of thecenter positioner 106. The desire is to achieve such a bend on the wholeperiphery of the booster 200.

For this, as shown in FIG. 1, the assembly device 100 is furnished witha gearing element 110 rotating the rollers 109 all about the booster200. The gearing element is itself rotated by a motor (not shown). Thegearing element 110 is furnished with two gear wheels 111 and 112. Thewheels 111 and 112 have a different number of teeth.

By means of the first wheel 111, the gearing element 110 rotates thewhole set of rollers 109A and 109B about the booster 200. The secondgear wheel 112 rotates an eccentric 118 imposing a periodic sinusoidalmovement on the rollers 109. Thus, by means of this eccentric 118, therollers 109 are not pressed continuously against the walls 205 and 209of the booster 200.

When the assembly device 100 is placed in motion, the rollers 109 rotatecontinuously all about the booster 200 and are pressed radially againstthe walls 205 and 209 of the booster 200 in a periodic intermittentmanner. The sets of rollers 109A and 109B are angularly out of phase.The angular-out-of-phase arrangement is such that it allows a pressureof the rollers 109A against the wall of the booster 200 to alternatewith a pressure of the rollers 109B.

In order to achieve a good swage, the desire is to press the rollers109A radially against the booster 200 before the rollers 109B.Specifically, the rollers 109A and 109B differ from one another in theirangles of attack. FIGS. 2 a and 2 b show that the rollers 109A and 109Bare all furnished respectively with a bevel 113A and 113B. A beveled cutforming the bevels 113A and 113B is made on a top face of the rollers109A and 109B. The shape of the bevels 113A and 113B is different.Specifically, an angle of attack 114A of the bevel 113A is greater thanthe angle of attack 114B of the bevel 113B. “Angle of attack” means theangle formed by the beveled cut of the bevels 113.

A first contact between the roller 109A and the end 208 of the wall 209of the cylinder 206 makes it possible to slightly bend the end 208 inthe direction of an axis C of the support 101. The roller 109B is thenpressed against the end 208 that is already partially bent. Since theangle of attack 114B is less than the angle of attack 114A, it ispossible to bend the end 208 slightly more in the direction of the axisC.

For example, the angle of attack 114A lies between 115° and 135°. Theangle of attack 114B, for its part, lies between 80° and 90°. In apreferred example, the angle of attack 114A is 120°. Thus, the end 208is folded 60° during the pass of the roller 109A. Then, during the passof the roller 109B, the end 208 is bent an additional 25°. Finally, theend 208 is virtually perpendicular to the axis of the center positioner106. The end 208 swages the end 104 while trapping the fold 211.

In the invention, such a swaging operation is performed over the wholeperiphery of the booster 200. The device 100 makes as many rotationsaround the booster 200 as necessary for the cylinder 206 to be attachedto the cover 203.

FIG. 1 shows a particular exemplary embodiment of the device making itpossible to rotate the rollers 109 and impart thereto a radiallyoscillating movement relative to an axis C of the support 101.

The gear wheel 111 of the gearing element 110 rotates a pinion 115. Abody 116 is attached to the pinion 115. The body 116 is thereforerotated by the rotation of the wheel 111. The body 116 is thus rotatedall around the support 101. The wheel 112 of the gearing element 110rotates a pinion 117. The pinion 117 is attached free in rotation to thebody 116. Thus, the pinion 117 rotates independently of the body 116.The rotations of the body 116 and of the pinion 117 depend respectivelyon the rotation of the wheel 111 and the wheel 112 of the gearingelement 110. The number of teeth of the wheel 111 is different from thenumber of teeth of the wheel 112. The body 116 and the pinion 117therefore do not rotate at the same speed. The pinion 117 rotates theeccentric 118 by means of a pinion 119. The eccentric 118 follows atleast partially an internal periphery of the body 116.

The rollers 109 are mounted on a top end of the eccentric 118. Theeccentric 118 is attached to the body 116. The rollers 109 are thereforerotated all about the booster 200. But since the eccentric 118 is alsoin contact with the pinion 117, the pinion 117 imposes a radialoscillating movement relative to the axis C of the support 101 on theeccentric 118 and the rollers 109.

This gives, in addition to a rotary movement of all the rollers 109about the booster 200, a radial oscillating movement of each of therollers 109 relative to the axis C of the support 101. The rollers 109are therefore periodically pressed against the wall of the booster 200and then separated therefrom. The angular-out-of-phase arrangementbetween the rollers 109A and the rollers 109B makes it possible to pressthe rollers 109A first against the wall of the booster 200. The rollers109B are pressed only after the rollers 109B have passed.

The invention claimed is:
 1. A device (100) for assembling a pneumaticbooster (200), comprising: a fixed cylindrical support (101) whoseinternal volume (102) is greater than the volume of a cover (203) of thebooster, the cover being housed in the support, a cylindrical cap (104)whose internal volume (107) is greater than the volume of a cylinder(206) of the booster, said cap imposing an axial load on the cylinder,and at least one set of rollers (109A, 109B), rotated by a motor, therollers rotating at least partially about the support wherein said fixedcylindrical support and said cylindral cap are arranged along a commonaxis with each of said fixed cylindrical support and cylindrical capbeing separably coupled with each other inorder to operate in engagingand disengaging motion and said at least one set of rollers having anaxial axis parallel with said common axis.
 2. The device according toclaim 1, wherein the at least one set of rollers (109A, 109B) comprisesa first set of rollers (109A) and a second set of rollers (109B), thetwo sets of rollers rotating at least partially about the support. 3.The device according to claim 2, further comprising a center positioner(106) lying on an upper end (103) of the fixed support, the cover lyingon the center positioner, the center positioner having a ring shape, aninternal diameter of the center positioner being approximately equal toa diameter of the booster cover.
 4. The device according to claim 3,wherein the first and second rollers are alternated.
 5. The deviceaccording to claim 4, wherein the first set of rollers is furnished withthree rollers, and the second set of rollers is furnished with threerollers, the first rollers being spaced at 120° from one another, andbeing spaced at 60° from the second rollers.
 6. The device according toclaim 5, wherein the first rollers are furnished with a bevel (113A),said bevel having an angle of attack (114A) lying between 115 and 135°,and the second rollers are each furnished with a bevel (113B), saidbevel having an angle of attack (114B) lying between 80and 90°.
 7. Thedevice according to claim 6, wherein the angle of attack of the bevelsof the first rollers is 120°, and the angle of attack of the bevels ofthe second rollers is 85°.
 8. The device according to claim 7, furthercomprising a gearing element (110) driving the rollers in rotation, andthe gearing element is furnished with two gear wheels, a number of teethof a first gear wheel (111) of the gearing element, driving in rotationthe two sets of rollers about the booster, being different from a numberof teeth of a second gear wheel (112) of said gearing element, thesecond wheel imposing by means of an eccentric (118) an oscillatingradial movement of the rollers relative to an axis (C) of the support.9. The device according to claim 1, wherein the cylindrical support(101) and the cylindrical cap (104) are arranged adjacent one another toencompass the booster.
 10. A device (100) for assembling a pneumaticbooster (200), comprising: a fixed cylindrical support (101) whoseinternal volume (102) is greater than the volume of a cover (203) of thebooster, the cover being housed in the support, a cylindrical cap (104)whose internal volume (107) is greater than the volume of a cylinder(206) of the booster, said cap imposing an axial load on the cylinder,and at least one set of rollers (109A, 109B), rotated by a motor, therollers rotating at least partially about the support; wherein the atleast one set of rollers (109A, 109B) comprises a first set of rollers(109A) and a second set of rollers (109B), the two sets of rollersrotating at least partially about the support; and further comprising acenter positioner (106) lying on an upper end (103) of the fixedsupport, the cover lying on the center positioner, the center positionerhaving a ring shape, an internal diameter of the center positioner beingapproximately equal to a diameter of the booster cover.
 11. The deviceaccording to claims 10, wherein the first and second rollers arealternated.
 12. The device according to claim 11, wherein the first setof rollers is furnished with three rollers, and the second set ofrollers is furnished with three rollers, the first rollers being spacedat 120° from one another, and being spaced at 60° from the secondrollers.
 13. The device according to claim 12, wherein the first rollersare furnished with a bevel (113A), said bevel having an angle of attack(114A) lying between 115 and 135°, and the second rollers are eachfurnished with a bevel (113B), said bevel having an angle of attack(114B) lying between 80 and 90°.
 14. The device according to claim 13,wherein the angle of attack of the bevels of the first rollers is 120°,and the angle of attack of the bevels of the second rollers is 85°. 15.The device according to claim
 14. further comprising a gearing element(110) driving the rollers in rotation, and the gearing element isfurnished with two gear wheels, a number of teeth of a first gear wheel(111) of the gearing element, driving in rotation the two sets ofrollers about the booster, being different from a number of teeth of asecond gear wheel (112) of said gearing element, the second wheelimposing by means of an eccentric (118) an oscillating radial movementof the rollers relative to an axis (C) of the support.